Scalable coding scheme for low latency applications

ABSTRACT

Fractional parts of quantized video coefficients are used as enhancement layers when encoding a video steam. This use of the fractional parts allows the reuse of decoding components.

FIELD OF THE INVENTION

This invention relates generally to video encoding and decoding, andmore particularly to a scalable coding scheme for video encoding anddecoding.

BACKGROUND OF THE INVENTION

Video is principally a series of still pictures, one shown after anotherin rapid succession, to give a viewer the illusion of motion. Before itcan be transmitted over a communication channel, analog video may needto be converted, or “encoded,” into a digital form. In digital form, thevideo data are made up of a series of bits called a “bitstream.” Whenthe bitstream arrives at the receiving location, the video data are“decoded,” that is, converted back to a viewable form. Due to bandwidthconstraints of communication channels, video data are often “compressed”prior to transmission on a communication channel. Compression may resultin a degradation of picture quality at the receiving end.

A compression technique that partially compensates for loss(degradation) of quality involves separating the video data into a “baselayer” and one or more “enhancement layers” prior to transmission. Thebase layer includes a rough version of the video sequence and may betransmitted using comparatively little bandwidth. The enhancement layerstypically capture the difference between the base layer and the originalinput video picture. Each enhancement layer also requires littlebandwidth, and one or more enhancement layers may be transmitted at thesame time as the base layer. At the receiving end, the base layer may berecombined with the enhancement layers during the decoding process. Theenhancement layers provide correction to the base layer, consequentlyimproving the quality of the output video. Transmitting more enhancementlayers produces better output video, but requires more bandwidth.

The enhancement layers may be ordered so that the most significantcorrection is made by the first enhancement layer, with subsequentenhancement layers providing less significant correction. In this way,the quality of the output video can be “scaled” by combining differentnumbers of the ordered enhancement layers with the base layer. Theprocess of using ordered enhancement layers to scale the quality of theoutput video is referred to as “Fine Granularity Scalability” (FGS) andmay result in a substantial saving of bandwidth.

Some compression methods and file formats have been standardized, suchas the Motion Picture Experts Group (MPEG) standards of theInternational Organization for Standardization. One of the MPEGstandards, MPEG-4, uses an FGS algorithm to produce a range of qualityof output video suitable for use with various bandwidths. However, theamount of processing required with MPEG-4 FGS renders it unsuitable forapplications that require low end-to-end delay, such asvideoconferencing.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a block diagram illustrating a video conferencing system inaccordance with the present invention;

FIG. 1B is a block diagram illustrating a video streaming system inaccordance with the present invention;

FIG. 2 is a block diagram illustrating a prior art encoding structure;

FIG. 3 is a block diagram illustrating one embodiment of an encodingstructure according to the invention;

FIG. 4 is a block diagram illustrating a prior art decoding structurecorresponding to the encoding structure of FIG. 2;

FIG. 5 is a block diagram illustrating a decoding structurecorresponding to the encoding structure of FIG. 3;

FIGS. 6A-C are block diagram illustrating alternate embodiments of adecoding structure according to the invention;

FIGS. 7A-C are block diagrams illustrating encoding structurescorresponding to the decoding structures of FIGS. 6A-C;

FIG. 8 is a flowchart of an method for performing the encoding operationof the encoding structures of FIGS. 7A-C;

FIGS. 9A-C are flowcharts of methods for performing the decodingoperations of decoding structures of FIG. 6A-C; and

FIG. 10 is a diagram of one embodiment of a computer system in which aencoder or decoder according to the invention may incorporated.

DETAILED DESCRIPTION OF THE INVENTION

In the following detailed description of embodiments of the invention,reference is made to the accompanying drawings in which like referencesindicate similar elements, and in which is shown by way of illustrationspecific embodiments in which the invention may be practiced. Theseembodiments are described in sufficient detail to enable those skilledin the art to practice the invention, and it is to be understood thatother embodiments may be utilized and that logical, mechanical,electrical, functional and other changes may be made without departingfrom the scope of the present invention. The following detaileddescription is, therefore, not to be taken in a limiting sense, and thescope of the present invention is defined only by the appended claims.

Two video systems in which embodiment of the invention may be practicedare shown in FIGS. 1A and 1B. FIG. 1A is a block diagram of a videoconferencing system 100 in which the participant's video system 101, 103contain an MPEG-4 FGS codec 105 that encodes and decodes video streamsin accordance with embodiments of the invention described below. Videosystem 101 is connected to video system 103 through an asymmetriccommunications link that has more bandwidth in the channel 119 fromvideo system 101 to video system 103 than the channel 125 from videosystem 103 to video system 101, such as an asymmetric digital subscriberline (ADSL) or digital cable connections. As shown, an encoder 107 inthe codec 105 at video system 101 encodes a video signal from a camera111 into a base layer bitstream and an enhancement layer bitstream andsends the bitstreams to a communications interface 115 for transmissionto the video system 103. The communications interface 115 transmits thelargest amount of bitstream data that can be handled by the channel 119.The bitstreams may be combined into a single bitstream through amultiplexer (not shown) before they are transmitted. When acommunications interface 117 at video system 103 receives the bitstream,the bitstream is de-muxed, if necessary, and the base and enhancementlayer bitstream are sent to a decoder 109 in the codec 105, where theyare decoded into a video picture that is shown on a display 121.Similarly, the encoder 107 in the code 105 at video system 103 encodes avideo signal from camera 123. However, because the channel 125 is oflower bandwidth than the channel 119, a communications interface 117 onvideo system 103 selects less bitstream data to transmit to video system101.

In a heterogeneous networking environment the bandwidth of the channelscan vary significantly but the scalability of MPEG-4 FGS enables thevideo systems 101, 103 to transmit the highest quality video given theavailable bandwidth. However, in a real-time video system, such as thevideo conferencing system of FIG. 1A, a low end-to-end latency cannot beachieved if the codec must perform processing-intensive calculations oneach end of the transmission. As described below, in one embodiment, thepresent invention reduces the amount of processing required to encodethe video stream by using a fractional part of existing quantized videocoefficients as frequency-ordered enhancement layers to eliminate aseparate frequency weighting component traditionally used to reduceflickering. For environments in which motion compensation is notcritical, such as video conferences, the use of the fractional part asthe frequency-ordered enhancement layers also allows the reuse ofdecoding components.

The embodiments of the present invention are not limited to use with lowlatency video systems but is equally applicable to streaming videosystems, such as illustrated in FIG. 1B. An encoder 133 in an encodingsystem (not shown) encodes a video signal from a camera 131 into baseand enhancement layer bitstreams, which are stored on a storage device135. When a user requests the video, a server 137 reads the bitstreamsfrom the storage device 135, determines the bandwidth of thecommunications link 139 to the playback computer 141, and transmits anamount of bitstream data that is supported by the bandwidth. A decoder143 in the playback system 141 decodes the bitstream to produce thevideo shown to the user on display 145. Incorporation of the inventionreduces the processing requirements of the encoder 133 and decoder 143and thus that of both the encoding and the playback systems whenproducing and displaying high quality video.

While various system configurations have been described to illustratethe use of encoder and decoders, it will be appreciated that theinvention is not limited to these configurations. For example, theencoding system and the server 137 of FIG. 1B may be the same ordifferent systems. Furthermore, any or all of the video systems, theencoding system, the server, and the playback system may be generalpurpose computers, such as described below in conjunction with FIG. 10,or specially-designed systems.

The use of the fractional part of the quantization as the enhancementlayer in an FGS codec is now described in conjunction with FIGS. 3 and5, with reference to prior art encoding and decoding structures in FIGS.2 and 4. The FGS encoding structure 200 of FIG. 2 encodes a series ofvideo frames 203 to produce a base layer bitstream 213 plus a bitstreamof one or more enhancement layers 237. A base layer encoding structure201 employs a discrete cosine transform (DCT) 207, quantization (Q) 209,and variable length coding (VLC) 211 components. The encoding structurealso includes a feedback “reconstruction ” loop that subtracts 205 areconstructed base layer from an incoming frame 203 to remove temporalredundancies from the incoming frames. The reconstruction loop performsan inverse quantization (IQ) 215 and inverse discrete cosine transform(IDCT) 217 on the output of Q 209 to reverse the IQ 215 and DCT 217operations. A clipping component 221 modifies the output of the IDCTcomponent 217 to within a valid range, if needed, and the output fromthe clipping component 221 is stored in a frame memory 223. The data inthe frame memory 223 is processed to compensate for motion (using motionestimation (ME) 225 and motion compensation (MC) 227 components) toproduce the reconstructed base layer.

An enhancement layer encoding structure 202 produces the enhancementlayers by subtracting 229 the clipping component output from theincoming frame 203 and transforming the difference into coefficients inthe DCT domain (DCT 231 ). When lower frequency layers are transmittedfirst, the flickering effect is reduced, and so a frequency weighting(FW) 233 shifts each DCT coefficient using a FW matrix to arrange theindividual enhancement layers in frequency order. The orderedenhancement layers are processed through a VLC 235 to produce theenhancement layer bitstream 237.

It can be shown that the FW matrix is equivalent to a quantizationmatrix with a stepsize of a power of two and that a quantization matrixthat satisfies the following equation is functionally equivalent to theFW matrix:

$\begin{matrix}{\frac{E( {{\Delta\; x}} )}{Qx} \geq {\frac{E( {{\Delta\; y}} )}{Qy}\mspace{14mu}{where}\mspace{14mu}{Qx}} \leq {Qy}} & (1)\end{matrix}$with Q_(x) and Q_(y) being the quantization stepsize of the low and highfrequency DCT coefficients, respectively, and Δx and Δy representing theremainder of low and high frequency DCT coefficients, respectively.Assuming a base layer quantization matrix having the above properties inthe Q component 209, and the IDCT 217 and DCT 231 having infiniteprecision, the fractional part of the quantized base layer DCTcoefficients is functionally equivalent to the output of the frequencyweighting component 233.

While a quantization matrix has been described that creates a fractionalpart equivalent to frequency-ordered enhancement layers, one of skill inthe art will immediately recognize that other embodiments of encodingstructures may require alternate quantization matrices that createfractional parts equivalent to enhancement layers ordered according toother criteria or enhancements layers that are not arranged in anyparticular order. Such alternate quantization matrices are consideredwithin the scope of the invention.

Thus, the enhancement layer encoding structure 202 can be modified asillustrated in FIG. 3. An appropriate quantization matrix isincorporated into Q 209 and the quantized base layer DCT coefficientsare parsed into their integer parts 305 and fractional parts 307. Theinteger parts 305 are input into the VLC 211 to produce a base layerbitstream 309 and into the reconstruction loop. The fractional parts 307are variable length encoded 235 in an enhancement layer encodingstructure 303 to produce an enhancement layer bitstream 311. Eachenhancement layer may be represented by one or more binary decimalpositions within each fractional part 307. The fractional parts 307 maynot be able to be represented by a finite number of binary digits andsome bits may need to be truncated. Therefore, in one embodiment, amaximum number to keep is based on the capacity of the system on whichthe encoding structure is implemented. In an alternate embodiment, asmany bits as possible are kept, which may vary from time to timedepending on the load on the system. It will be appreciated that thestepsize of the quantization matrix may be any integer value N, and theresulting integer part will be a value from 0 to N−1.

A prior art decoding structure 400 corresponding to the prior artencoding structure 200 is illustrated in FIG. 4. A base layer decodingstructure 401 reverses the operations of the encoding structure 200 onthe base layer bitstream 213 using a variable length decoder (VLD) 403,inverse quantization (IQ) 405 and an inverse discrete cosine transform(IDCT) 407. A feedback “prediction ” loop adds 409 some or all of thetemporal redundancies removed in the reconstruction loop in the baselayer encoding structure 201 to create a restored base layer. Clipping411 is performed on the restored base layer and the result is(optionally) output as the base layer 413 and stored in a frame memory415. A motion compensation (MC) component 417 is also included in theprediction loop. The enhancement bitstream 237 is decoded in structure403 using a VLD 419, a bit plane shifter (BP shift) 421 to reverse theFW operation 233 and an IDCT 423. The base layer 413 is added 425 to theresulting enhancement layers, clipped 427, and output as the video frame429.

Because the enhancement bitstream 311 produced by the encoder 300 inFIG. 3 is derived from the fractional parts of the quantized DCTcoefficients computed at the base layer, the enhancement layer decodingstructure 403 can be modified as shown in FIG. 5. After variable lengthdecoding 419, an inverse quantization (IQ) component 507 is used toreverse the quantization 209 that produced the fractional parts. The IQ507 replaces the BP shift component 421 shown in FIG. 4.

It will be appreciated that corresponding DCT/IDCT, Q/IQ and VLC/VLDcomponents are used within the encoding/decoding structures illustratedherein. Additionally, common components are given different referencenumbers to indicate different instances of a component. For example, oneof skill in the art will immediately recognize that IQ 507 and IQ 405 inFIG. 5 perform the same operations but cannot be the same IQ componentbecause the enhancement layer signal would flow into the prediction loopand result in error drifting.

When motion compensation for the video frames is not critical, theencoding and decoding structures of FIGS. 3 and 5 may be modifiedfurther as illustrated in FIGS. 6A-C and 7A-C, and the particularembodiments illustrated in FIGS. 6B and 6C allow the reuse of commondecoding components without causing error drifting. In each of thefollowing embodiments, the decoding structure is first described andthen the corresponding encoding structure. Clipping components are notshown for ease in illustration but one of skill in the art willimmediately understand where clipping would be applied.

Assuming zero-motion vectors, the prediction loop in the base layerdecoding structure 501 can be treated as a linear time invariant loopand does not require the MC component 417, resulting in the base layerdecoding structure 601 illustrated FIG. 6A. Furthermore, the additioncomponent 425 can be moved into the base layer decoding structure 601,eliminating output of the base layer alone when there are enhancementlayers present. The corresponding encoding structure 700 illustrated inFIG. 7A eliminates the ME 225 and MC 227 components in thereconstruction loop since the reconstruction loop is similarly treatedas a linear time invariant loop.

In another embodiment, the exchange law of linear time invariant systemsallows the prediction loop in the base layer decoding structure to beexchanged with the IDCT 407 as illustrated in FIG. 6B. Because the IDCT407 and the IDCT 423 of FIG. 6A are equivalent, exchanging theprediction loop with the IDCT 407 allows the use of a single IDCTwithout incurring error drifting problems. The corresponding encodingstructure 710 is shown in FIG. 7B, in which the temporal redundanciesare removed from the incoming frames 203 after the frames have beentransformed into the DCT domain.

In a further embodiment, the prediction loop is moved before the IQ 405as illustrated in FIG. 6C to allow reuse of the IQ 405 in the decodingstructure 620 without introducing error drifting. Because the IQ 405 isnot a linear time invariant system, the quantization parameters Q_(p)used to encode the bitstreams 725, 727 (FIG. 7C) are transmitted to thedecoding structure so the time variations of IQ 405 are known to thedecoding structure 620. It will be appreciated that having Q_(p) fixedor smoothly changing will enhance the efficiency of the decodingstructure 620. A corresponding encoding structure 720 illustrated inFIG. 7C removes the temporal redundancies from the incoming frames 203after the frames have been transformed and quantized.

Next, the particular methods of the invention are described in terms ofexecutable instructions with reference to a series of flowcharts.Describing the methods by reference to a flowchart enables one skilledin the art to develop such instructions to carry out the methods withinsuitably configured processing units. The executable instructions may bewritten in a computer programming language or may be embodied infirmware logic. Furthermore, it is common in the art to speak ofexecutable instructions as taking an action or causing a result. Suchexpressions are merely a shorthand way of saying that execution of theinstructions by a computer causes the processor of the computer toperform an action or a produce a result.

FIGS. 8 and 9A-C illustrate the methods to be performed by a system toimplement the operations of the encoding and decoding structures of theinvention previously described. The embodiments of an encoding methodare illustrated in a flowchart in FIG. 8, including all the acts(blocks) from 801 until 819. The embodiments of decoding methods areillustrated in flowcharts in FIGS. 9A-C, including all the acts from 901until 935.

Referring first to FIG. 8, the acts that cause a system to perform theoperations of the encoding structures of FIGS. 3 and 7A-C are shown asFGS encoding method 800. Because the encoding structures of FIGS. 3 and7A-C remove the temporal redundancies at different points in theencoding process, phantom blocks 801, 805 and 815 in FIG. 8 are used torepresent the removal operation. For FIGS. 3 and 7A, temporal redundancyremoval is performed at block 801; for FIG. 7B, at block 805; and forFIG. 7C, at block 815. The incoming frame is transformed (block 803) andthe transformed result is quantized (block 807). The result of thequantization is parsed at block 809 into its fractional parts and itsinteger parts. The fractional parts are encoded (block 811), and theencoded fractional parts are output as the enhancement layer bitstream(block 813). The integer parts are encoded (block 817), and the encodedinteger parts are output as the base layer bitstream (block 819).

An FGS decode method 900 is illustrated in FIG. 9A that causes a systemto perform the operations of the decode structures shown in FIGS. 5 and6A. The enhancement layers are decoded (block 901), an inversequantization (block 903) and an inverse transformation (block 905) areapplied. The output of block 905 is applied into the base layer at block915 as described below. Similarly, the base layer is decoded (block 907)and an inverse quantization (block 909) and an inverse transformation(block 911) applied. Some or all of the base layer temporal redundanciesare restored to reconstruct the base layer (block 913). At block 915,the enhancement layers from block 905 are applied to the reconstructedbase layer. The resulting video stream is output at block 917.

Turning now to FIG. 9B, an FGS decode method 920 is described thatcauses a system to perform the operations of the decoding structures ofFIG. 6B. Similar to method 900, method 920 decodes the enhancement layerdata stream at block 901 and applies an inverse quantization at block903. The output of block 903 is applied to the base layer at block 915as described below. As in FIG. 9A, the base layer bitstream is decodedat block 907 and the inverse quantization is applied at block 909. Thebase layer temporal redundancies are restored at block 913 and theenhancement layers from block 903 are applied to the modified base layerat block 915. In this case, the inverse transformation is applied to thecombined base layer and enhancement layers (block 921) and the result isoutput as the video stream (block 923).

As shown in FIG. 9C, an FGS decode method 930 that that causes a systemto perform the operations of the decoding structures in FIGS. 6C decodesthe enhancement layer data stream at block 909, leaving the inversequantization and the inverse transformation to be applied to thecombined base layer and enhancement layers at blocks 931 and 933, withthe resulting video stream being output at 935. Blocks 907, 913 and 915perform the processes described above for those blocks in FIGS. 9A and9B.

The following description of FIG. 10 is intended to provide an overviewof computer hardware environments in which the encoding/decodingstructures and methods of the invention can be implemented, but is notintended to limit the applicable environments. FIG. 10 shows one exampleof a conventional computer system 1001 containing a processing unit 1005and a memory 1009 coupled to the processor 1005 by a bus 1007. Memory1009 can be dynamic random access memory (DRAM) and can also includestatic RAM (SRAM). The bus 1007 couples the processor 1005 to the memory1009 and also to non-volatile storage 1015, to display controller 1011,to the input/output (I/O) controller 1017, and to a modem or networkinterface 1003. The display controller 1011 controls in the conventionalmanner a display on a display device 1013 which can be a cathode raytube (CRT) or liquid crystal display. The input/output devices 1019 caninclude a keyboard, disk drives, printers, a scanner, and other inputand output devices, including a mouse or other pointing device. Theinput/output devices 1019 may include a digital image input device, suchas a digital camera, that is coupled to the I/O controller 1017 in orderto allow images from the digital image input device to be input into thecomputer system 1001. The modem/network interface 1003 enables thecomputer 1001 to communicate with other computers or devices on anetwork 10021. The display controller 1011, the I/O controller 1017, andthe modem/network interface 1003 can be implemented with conventionalwell known technology. The non-volatile storage 1015 is often a magnetichard disk, an optical disk, or another form of storage for large amountsof data. Some of this data is often written, by a direct memory accessprocess, into memory 1009 during execution of software in the computersystem 1001. One of skill in the art will immediately recognize that theterm “computer-readable medium” or “machine-readable medium” includesany type of storage device that is accessible by the processor 1005 andalso encompasses a carrier wave that encodes a data signal.

It will be appreciated that the computer system 1001 is one example ofmany possible computer systems which have different architectures. Oneof skill in the art will immediately appreciate that the invention canbe practiced with other computer system configurations, includinghand-held devices, multiprocessor systems, microprocessor-based orprogrammable consumer electronics, networked personal computers,minicomputers, mainframe computers, and the like. A typical computersystem will usually include at least a processor, memory, and a buscoupling the memory to the processor.

Although specific embodiments have been illustrated and describedherein, it will be appreciated by those of ordinary skill in the artthat any arrangement which is calculated to achieve the same purpose maybe substituted for the specific embodiments shown. This application isintended to cover any adaptations or variations of the presentinvention. For example, although the invention is described in terms ofparticular FGS encoding and decoding structures, the concept ofreplacing the enhancement layer frequency weighting matrix with the baselayer quantization matrix is applicable to other coding algorithms.Therefore, it is manifestly intended that this invention be limited onlyby the following claims and equivalents thereof.

1. A method comprising: quantizing coefficients into quantized values,each quantized value for a corresponding coefficient having an integerpart and a fractional part, the integer part representing a base layerfor the corresponding coefficient and the fractional part representingenhancement layers for the corresponding coefficient, the coefficientsrepresenting input data; and encoding the fractional parts into anenhancement layer bitstream.
 2. The method of claim 1 furthercomprising: encoding the integer parts into a base layer bitstream. 3.The method of claim 1 further comprising: transforming an input into thecoefficients.
 4. The method of claim 3 further comprising: removingtemporal redundancies exhibited by the input.
 5. The method of claim 1,wherein the enhancement layers are frequency ordered.
 6. A methodcomprising: decoding an enhancement layer bitstream into quantizedfractional values representing enhancement layers, each quantizedfractional value being a fractional part of a quantization valuegenerated from coefficients representing input data; applying an inversequantization to the quantized fractional values to create coefficientsrepresenting the enhancement layers; applying an inverse transformationto the coefficients to create the enhancement layers; and combining theenhancement layers with a base layer.
 7. The method of claim 6 furthercomprising: adding temporal redundancies to the base layer.
 8. A methodcomprising: decoding an enhancement layer bitstream into quantizedfractional values representing enhancement layers, each quantizedfractional value being a fractional part of a quantization valuegenerated from coefficients representing input data; applying an inversequantization to the quantized fractional values to create coefficientsrepresenting the enhancement layers; combining the coefficientsrepresenting the enhancement layers with coefficients representing abase layer; and applying an inverse transformation to the combinedcoefficients.
 9. The method of claim 8 further comprising: addingtemporal redundancies to the coefficients representing the base layer.10. A method comprising: decoding an enhancement layer bitstream intoquantized fractional values representing enhancement layers, eachquantized fractional value being a fractional part of a quantizationvalue generated from coefficients representing input data; combining thequantized fractional values representing enhancement layers withquantized integer values representing a base layer; applying an inversequantization to the combined quantized values to create coefficients;and applying an inverse transformation to the coefficients.
 11. Themethod of claim 10 further comprising: adding temporal redundancies tothe quantized integer values representing the base layer.
 12. Acomputer-readable medium embodied with a computer program, which whenexecuted by a computer, causes the computer to perform operationscomprising: quantizing coefficients into quantized values, eachquantized value for a corresponding coefficient having an integer partand a fractional part, the integer part representing a base layer forthe corresponding coefficient and the fractional part representingenhancement layers for the corresponding coefficient, the coefficientsrepresenting input data; and encoding the fractional parts into anenhancement layer bitstream.
 13. The computer-readable medium of claim12, wherein the operations further comprise: encoding the integer partsinto a base layer bitstream.
 14. The computer-readable medium of claim12, wherein the operations further comprise: transforming an input intothe coefficients.
 15. The computer-readable medium of claim 14, whereinthe operations further comprise: removing temporal redundanciesexhibited by the input.
 16. The computer-readable medium of claim 12,wherein the enhancement layers are frequency ordered.
 17. Acomputer-readable medium embodied with a computer program, which whenexecuted by a computer, cause the computer to perform operationscomprising: decoding an enhancement layer bitstream into quantizedfractional values representing enhancement layers, each quantizedfractional value being a fractional part of a quantization valuegenerated from coefficients representing input data; applying an inversequantization to the quantized fractional values to create coefficientsrepresenting the enhancement layers; applying an inverse transformationto the coefficients to create the enhancement layers; and combining theenhancement layers with a base layer.
 18. The computer-readable mediumof claim 17, wherein the operations further comprise: adding temporalredundancies to the base layer.
 19. A computer-readable medium embodiedwith executable program instructions, which when executed by aprocessing unit of a computer, cause the processing unit to performoperations comprising: decoding an enhancement layer bitstream intoquantized fractional values representing enhancement layers, eachquantized fractional value being a fractional part of a quantizationvalue generated from coefficients representing input data; applying aninverse quantization to the quantized fractional values to createcoefficients representing the enhancement layers; combining thecoefficients representing the enhancement layers with coefficientsrepresenting a base layer; and applying an inverse transformation to thecombined coefficients.
 20. The computer-readable medium of claim 19,wherein the operations further comprise: adding temporal redundancies tothe coefficients representing the base layer.
 21. A computer-readablemedium providing executable program instructions, which when executed bya processing unit of a computer, cause the processing unit to performoperations comprising: decoding an enhancement layer bitstream intoquantized fractional values representing enhancement layers, eachquantized fractional value being a fractional part of a quantizationvalue generated from coefficients representing input data; combining thequantized fractional values representing enhancement layers withquantized integer values representing a base layer; applying an inversequantization to the combined quantized values to create coefficients;and applying an inverse transformation to the coefficients.
 22. Thecomputer-readable medium of claim 21, wherein the operations furthercomprise: adding temporal redundancies to the quantized integer valuesrepresenting the base layer.
 23. A system comprising: a processor; amemory coupled to the processor though a bus; and an encoding processexecuted from the memory by the processor to cause the processor toquantize coefficients into quantized values, each quantized value for acorresponding coefficient having an integer part and a fractional part,the integer part representing a base layer for the correspondingcoefficient and the fractional part representing enhancement layers forthe corresponding coefficient, the coefficients representing input data,and to encode the fractional parts into an enhancement layer bitstream.24. The system of claim 23, wherein the encoding process further causesthe processor to encode the integer parts into a base layer bitstream.25. The system of claim 23, wherein the encoding process further causesthe processor to transform an input into the coefficients.
 26. Thesystem of claim 25, wherein the encoding process further causes theprocessor to remove temporal redundancies exhibited by the input. 27.The system of claim 23, wherein the enhancement layers are frequencyordered.
 28. A system comprising: a processor; a memory coupled to theprocessor though a bus; and a decoding process executed from the memoryby the processor to cause the processor to decode an enhancement layerbitstream into quantized fractional values representing enhancementlayers, each quantized fractional value being a fractional part of aquantization value generated from coefficients representing input data,to apply an inverse quantization to the quantized fractional values tocreate coefficients representing the enhancement layers, to apply aninverse transformation to the coefficients to create the enhancementlayers, and to combine the enhancement layers with a base layer.
 29. Thesystem of claim 28, wherein the decoding process further cause theprocessor to add temporal redundancies to the base layer.
 30. A systemcomprising: a processor; a memory coupled to the processor though a bus;and a decoding process executed from the memory by the processor tocause the processor to decode an enhancement layer bitstream intoquantized fractional values representing enhancement layers, eachquantized fractional value being a fractional part of a quantizationvalue generated from coefficients representing input data, to apply aninverse quantization to the quantized fractional values to createcoefficients representing the enhancement layers, to combine thecoefficients representing the enhancement layers with coefficientsrepresenting a base layer, and to apply an inverse transformation to thecombined coefficients.
 31. The system of claim 30, wherein the decodingprocess further cause the processor to add temporal redundancies to thecoefficients representing the base layer.
 32. A system comprising: aprocessor; a memory coupled to the processor though a bus; and andecoding process executed from the memory by the processor to cause theprocessor to decode an enhancement layer bitstream into quantizedfractional values representing enhancement layers, each quantizedfractional value being a fractional part of a quantization valuegenerated from coefficients representing input data, to combine thequantized fractional values representing enhancement layers withquantized integer values representing a base layer, to apply an inversequantization to the combined quantized values to create coefficients,and to apply an inverse transformation to the coefficients.
 33. Thesystem of claim 32, wherein the decoding process further cause theprocessor to add temporal redundancies to the quantized integer valuesrepresenting the base layer.
 34. An apparatus comprising: atransformation component coupled to an input to create coefficients fromthe input; a quantization component coupled to the transformationcomponent to create quantized values from the coefficients, eachquantized value for a corresponding coefficient having an integer partand a fractional part, the integer part representing a base layer forthe corresponding coefficient and the fractional part representingenhancement layers for the corresponding coefficient; a first encodingcomponent coupled to the quantization component to create a base layerbitstream from the integer parts; and a second encoding componentcoupled to the quantization component to create a an enhancement layerbitstream from the fractional parts.
 35. The apparatus of claim 34further comprising: a reconstruction loop coupled to the quantizationcomponent and to the input to remove temporal redundancies from theinput.
 36. The apparatus of claim 34 further comprising: areconstruction loop coupled to the quantization component and to thetransformation component to remove temporal redundancies from thecoefficients.
 37. The apparatus of claim 34 further comprising: areconstruction loop coupled between the quantization component and thefirst encoding component to remove temporal redundancies from theinteger parts.
 38. The apparatus of claim 34, wherein the enhancementlayers are frequency ordered.
 39. An apparatus comprising: a decodingcomponent coupled to an enhancement layer bitstream to create quantizedfractional values representing enhancement layers from the enhancementlayer bitstream, each quantized fractional value being a fractional partof a quantization value generated from coefficients representing inputdata; an inverse quantization component coupled to the decodingcomponent to create coefficients from the quantized fractional values; afirst inverse transformation component coupled to the inversequantization component to create the enhancement layers from thecoefficients; and an addition component coupled to the first inversetransformation component and further to a second inverse transformationcomponent to combine the enhancement layers with a base layer from thesecond inverse transformation component.
 40. The apparatus of claim 39further comprising: a prediction loop coupled to the second inversetransformation component to add temporal redundancies to the base layer.41. An apparatus comprising: a decoding component coupled to anenhancement layer bitstream to create quantized fractional valuesrepresenting enhancement layers from the enhancement layer bitstream,each quantized fractional value being a fractional part of aquantization value generated from coefficients representing input data;a first inverse quantization component coupled to the decoding componentto create coefficients from the quantized values; an addition componentcoupled to the first inverse quantization component and further to asecond inverse quantization component to combine the coefficients fromthe first inverse quantization component with coefficients from thesecond inverse quantization; and an inverse transformation componentcoupled to the addition component to create combined enhancement andbase layers from the coefficients.
 42. The apparatus of claim 41 furthercomprising: a prediction loop coupled to the second inverse quantizationcomponent to add temporal redundancies to the coefficients from thesecond quantization component.
 43. An apparatus comprising: a firstdecoding component coupled to an enhancement layer bitstream to createquantized fractional values representing enhancement layers from theenhancement layer bitstream, each quantized fractional value being afractional part of a quantization value generated from coefficientsrepresenting input data; an addition component coupled to the firstdecoding component and further to a second decoding component to combinethe quantized fractional values from the first decoding component withquantized integer values from the second decoding component; an inversequantization component coupled to the addition component to createcoefficients from the quantized values; and an inverse transformationcomponent coupled to the inverse quantization component to createcombined enhancement and base layers from the coefficients.
 44. Theapparatus of claim 43 further comprising: a prediction loop coupled tothe second decoding component to add temporal redundancies to thequantized integer values.